PCB Trace Width Calculator

A copper trace on a circuit board can only carry so much current before it heats up, and undersizing it risks a burned track. This calculator sizes the trace for you using the widely used IPC 2221 relationship. Enter the current in amps, the copper weight or thickness in ounces per square foot, and the temperature rise you will accept above ambient, then choose whether the trace runs on an external or an internal layer, since internal traces cool more slowly and need to be wider. The tool returns the minimum trace width in millimetres and mils. External traces can be narrower because they shed heat to the air, while inner layer traces are derated. This is essential for power rails, motor drivers and anything carrying meaningful current. Enter your values and read a safe width instantly. Everything runs locally in your browser, so it is fast and private.